1. Field of the Invention
The invention relates to an arrangement for fire control of a gun, comprising a tracking radar unit with radar transmitter/receiver and antenna means, mounted directly on the gun so that the axis of the antenna means forms a given angle with the axis of the fire tube, and producing control signals for the set motors of the fire tube in order to, after locking on a target, bring the radar axis and thereby the axis of the fire tube to follow the target by influencing the said set motors in a closed servo loop.
2. Description of the Invention
By mounting the tracking radar unit directly on the gun an improved all-weather-capability of gun fire control is achieved. However, there is a mechanical influence on the radar at firing, caused by compression waves from the mouth of the fire tube, recoil and damping forces. This produces a mechanical environment with large accelerations over a wide frequency range.
In a previously proposed system, in which the tracking radar is included in the servo loop of the gun, the gun is directed to a predicted forward point at the firing moment. There is then no requirement for simultaneous radar tracking and firing, but this requires that the compression waves at fire do not influence the radar during the tracking phase.
However, in certain applications it is advantageous to utilize the tracking radar also during fire. It should furthermore withstand the operative environment, involving the influences of vibration, ice, snow, rain, sand, flushing water and sun irradiation.
Under all these conditions it should maintain high accuracy and large operating range, and furthermore have multi-target (MTI) tracking capability.
A further objective is that it should be difficult to discover the radar by detection of IR-radiation.
It is assumed that the firing tube and the radar axis are parallel or have predictable static and dynamic deviations. Any such deviation which is unknown produces an error contribution from the radar.
The error contribution of the radar can be described in terms of its resolution and accuracy.
By resolution is meant the ability of the radar to discriminate between two adjacent targets. The resolution ability is measured laterally and in range. The lateral resolution is substantially the same as the lobe angle in the horizontal plane. The range resolution is a function of the radar pulse length.
By accuracy is meant the ability of the radar to determine the position of a target. The accuracy can be better than the resolution. In other words a target can be localized with errors which are smaller than the lobe width and pulse length, respectively.
The accuracy of a radar is to a large extent determined by the radar antenna. A radar antenna which is deformed by compression waves, locally heated by sun irradiation, influenced by ice coating etc, produces erroneous angular information. The determination of the position of the target will then also be erroneous.